1. Field of the Invention
The present invention relates to a resistive composition to be used for a resistor to detect electric currents that flow in the current detecting circuits or the like, a resistor using the same, and a making method thereof.
2. Description of the Related Art
With a reduction in the size of the electronic apparatus, electronic components, especially chip components used in such apparatus have been required to be more compact in size. For the purpose of detecting electric currents that flow in the electronic circuits and/or power circuits of an equipment or the like, chip components having low resistance value and low temperature coefficient of resistance (TCR) have been needed.
Conventional resistors have used resistive element such as silver (Ag)-palladium (Pd), or copper (Cu)-nickel (Ni) alloy so as to obtain the low resistance characteristic. Some resistors use wire rods made of copper (Cu)-manganese (Mn)-tin (Sn), or materials obtained by processing the wire rods into a foil, which are a resistive material having a low resistivity and low temperature coefficient of resistance, as disclosed in, for example, Laid-open Japanese Patent Application No. 2001-143901.
A current detecting chip resistor, which uses as a resistive composition copper-nickel alloy, copper-manganese-tin based alloys, or the like, and which controls deterioration of electric current detection accuracy due to the resistor temperature variation, has been proposed and, for example, is disclosed in Laid-open Japanese Patent Application No. 2002-50501.
In the case of the above-mentioned resistive element made of silver-palladium alloy contains no cadmium. However, since the binder glass contains lead, which is a harmful substance, environmental problems will arise. In the case of commercially available resistive element comprising above-mentioned elements, its characteristics are determined by itself.
A resistor utilizing copper-manganese-tin based alloys as disclosed in Laid-open Japanese Patent Application No. 2001-143901 uses lead as a cladding material, therefore, that resistor causes environmental problems like the above-mentioned resistive element does.
As with a chip resistor using copper-nickel alloy or the like as a resistive element, as disclosed in Laid-open Japanese Patent Application No. 2002-50501, in the case of copper-nickel composition resistive element, since the intrinsic property of copper, namely, its resistance value and the TCR (temperature coefficient of resistance) is dominant, the TCR increases as the resistance value decreases. Due to this, the resistive element cannot obtain the desired property (electric current detection precision).
Such examples show the following properties. When the copper-nickel composition is 60:40, the sheet resistance is 35 mΩ/□, and the TCR is 50×10−6/k. Additionally, when the copper-nickel composition is 90:10, the sheet resistance is 15 mΩ/□, and the TCR is 1200×10−6/K.
This invention is provided by taking the above-mentioned problems into account; its objective is to provide a low TCR resistive composition having low resistance value and containing no substance which is harmful to the environment, a resistor using the same, and making method thereof.